Hemispherical shoes used for swash plate compressors have been conventionally known. The hemispherical shoe includes a spherical portion in sliding contact with a hemispherical concave portion on a piston side, and an end surface portion in sliding contact with a swash plate (for example, Patent Literatures 1 to 4).
Recently, there has been a need for swash plate compressors for automobiles to be reduced in cost, be compatible with a new refrigerant, or the like. The swash plate compressors are particularly required to be more efficient.
To this end, the following improvements in the shoe have been proposed respectively in Patent Literatures 1 to 4. That is, in Patent Literature 1, the surface roughness of a sliding portion and the surface roughness of a non-sliding portion in the spherical portion of the hemispherical shoe are made different from each other. Patent Literature 2 proposes that the spherical portion has a stepped tapered surface. Also, Patent Literature 3 proposes that the outer peripheral edge of the hemispherical shoe is largely removed over the entire circumference to thereby form a cylindrical portion. Furthermore, Patent Literature 4 proposes that an oil groove having a spiral shape or the like is formed in the spherical portion of the hemispherical shoe.